When a file can be edited a new menu item called 'edit' will appear when clicking a file's diamond. Clicking this and the confirmation button will take you to a page where you can edit the contents of that file. Before saving you are given the option of converting spaces to tabs. When this checkbox is checked every four (4) spaces are converted to tabs.

The standard 'Save' button will save a copy of the file (overwriting the old copy) without leaving the edit window, allowing you to keep editing. The 'Save Exit' button will save the file and return you to the file listing.